Tables for
Volume F
Crystallography of biological macromolecules
Edited by E. Arnold, D. M. Himmel and M. G. Rossmann

International Tables for Crystallography (2012). Vol. F, ch. 10.1, pp. 246-247   | 1 | 2 |

Section Temperature calibration

H. Hopea* and S. Parkinb

aDepartment of Chemistry, University of California, Davis, One Shields Ave, Davis, CA 95616–5295, USA, and bDepartment of Chemistry, University of Kentucky, Lexington, Kentucky, USA
Correspondence e-mail: Temperature calibration

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Measurement of the temperature at the crystal site with sensing devices that require attached leads is very difficult, mainly because of heat conduction along the leads. It is usually necessary to loop the leads into the delivery nozzle.

Both Si diodes and Pt resistance sensors have become sufficiently miniaturized to make them preferred choices at the lowest temperatures. Thermocouples are acceptable above about 80 K. A reliable method of calibration makes use of the known temperature of a phase transition of a crystal in the normal data-collection position. For example, KH2PO4 (often referred to as KDP) has a sharp transition at 123 K from tetragonal to orthorhombic, and is commonly used. Another possibility is KH2AsO4, which has a corresponding phase transition at 95 K.

Two readout temperatures suffice, one at room temperature and one at the phase transition. The difference between readout temperature and crystal-site temperature can be assumed to vary linearly with T, so interpolation or extrapolation is simple.

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